Digital Camera Buyer's Guide: DSLR - Comments

In summary: I replied about your SLT example because, while it's true that SLTs have lower throughput than a traditional SLR, they are not mirrorless cameras, so I don't think...In summary, Andy Resnick submitted a new PF Insights post that discusses the advantages and disadvantages of digital SLRs with and without a reflex mirror. He also mentions that mirrorless cameras have a decreased optical throughput due to the light being redirected to the digital viewfinder.
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Andy Resnick
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Andy Resnick submitted a new PF Insights post

Digital Camera Buyer's Guide: DSLR

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Continue reading the Original PF Insights Post.
 
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Nice Insight Andy.

One thing I wonder about is why there is still an "R" in DSLR, now that we don't use film. Is there any advantage to not having the sensor exposed all the time? I can't think of many disadvantages, like the mirror vibrations you discuss yourself.
 
  • #3
DrClaude said:
Nice Insight Andy.

One thing I wonder about is why there is still an "R" in DSLR, now that we don't use film. Is there any advantage to not having the sensor exposed all the time? I can't think of many disadvantages, like the mirror vibrations you discuss yourself.
A few reasons (by no means exhaustive) why the reflex mirror/optical viewfinder still survives today:
  1. Optical viewfinder still has fastest response and potentially best color/resolution
  2. Off-sensor phase detect AF (receive their light through a semi-silvered reflex mirror and sub mirror) still best for moving/unpredictable subjects
  3. Similarly, off-sensor exposure meters (including TTL flash meters) can be useful
  4. Optical viewfinder doesn't eat batteries
Also, reasons not to have the sensor exposed all the time include heat/image noise, blooming, etc.

Obviously, EVFs have many unique advantages, and most of their disadvantages relative to a reflex mirror/optical viewfinder are diminishing as EVFs continue to improve.
 
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DrClaude said:
Nice Insight Andy.

One thing I wonder about is why there is still an "R" in DSLR, now that we don't use film. Is there any advantage to not having the sensor exposed all the time? I can't think of many disadvantages, like the mirror vibrations you discuss yourself.
Good question. If I understand you, the sensor can't be exposed all the time, because then there's no way to set an exposure time. Mirrorless cameras have an electronic mechanism to 'wipe' the sensor prior to an exposure, and the main advantage to mirrorless systems is as you say- there's no mirror that moves, not only reducing vibrations but also decreasing the distance between lens mount and sensor, allowing for smaller lenses. Mirrorless cameras can easily use lenses designed for rangefinder cameras.

On the other hand, mirrorless cameras have a decreased optical throughout, because some of the light is permanently re-directed to the (digital) viewfinder. I don't know exact numbers, but AFAIK, this represents about a half-stop of light lost.
 
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Andy Resnick said:
On the other hand, mirrorless cameras have a decreased optical throughout, because some of the light is permanently re-directed to the (digital) viewfinder. I don't know exact numbers, but AFAIK, this represents about a half-stop of light lost.
Wait, doesn't the EVF usually get fed by the image sensor itself?
 
  • #8
Andy Resnick said:
I expect different manufacturers have different approaches. Often, there is a pellicle beamsplitter that directs some light to the autofocus sensor:

https://qph.ec.quoracdn.net/main-qimg-4af617c02795fb9260f69dbaded8ddf9-c?convert_to_webp=true
That depicts the so-called SLT (Translucent instead of Reflex) configuration, used by Sony and previously by Canon to remove the need for flipping the mirror at a small cost to the light transmitted to the sensor. In other respects it is essentially the same as a traditional AF SLR and provides an optical viewfinder.
 
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olivermsun said:
That depicts the so-called SLT (Translucent instead of Reflex) configuration, used by Sony and previously by Canon to remove the need for flipping the mirror at a small cost to the light transmitted to the sensor. In other respects it is essentially the same as a traditional AF SLR and provides an optical viewfinder.

Exactly.
 
  • #10
Andy Resnick said:
Exactly.
Hmm, I don't understand why you chose this example then. The SLT is actually an SLR with a Pellicle mirror and an optical viewfinder, so it doesn't explain why mirrorless cameras should lose a fraction of a stop to the EVF.
 
  • #11
olivermsun said:
Hmm, I don't understand why you chose this example then. The SLT is actually an SLR with a Pellicle mirror and an optical viewfinder, so it doesn't explain why mirrorless cameras should lose a fraction of a stop to the EVF.

I think you missed my point- my point is that the throughput is lower on a mirrorless camera as compared to either a reflex or rangefinder camera, it's less relevant where the re-directed light goes.
 
  • #12
Andy Resnick said:
I think you missed my point- my point is that the throughput is lower on a mirrorless camera as compared to either a reflex or rangefinder camera, it's less relevant where the re-directed light goes.
I think I got your point, but I am disagreeing that the "throughput" of a mirrorless camera has to be any different from that of a reflex or rangefinder camera.

I replied about your SLT example because, while it's true that SLTs have lower throughput than a traditional SLR, they are not mirrorless cameras, so I don't think they are a relevant example.

Finally, I do think it's relevant to explain where the re-directed light goes. If, as on a modern mirrorless camera, the light isn't re-directed anywhere but it goes straight to the image sensor, just as it does in a digital rangefinder or an SLR in "live view" mode with the mirror flipped up, then why would the mirrorless camera have any lower throughput than the others?
 
  • #13
olivermsun said:
I think I got your point, but I am disagreeing that the "throughput" of a mirrorless camera has to be any different from that of a reflex or rangefinder camera.

Maybe it would be helpful to identify the specific camera you are thinking about?
 
  • #14
The Sony A6xxx and A7 series are current mirrorless cameras with very similar sensors to several (e.g., Nikon) DSLRs, and they show low-light performance very comparable to same-format DSLRs. Olympus m4/3 cameras also perform just fine, with allowance for the smaller sensor size.

However, empirical results aside, it's probably equally or more important to understand what are the fundamental constraints of various configurations and what creates those constraints.
 
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  • #15
olivermsun said:
The Sony A6xxx and A7 series are current mirrorless cameras with very similar sensors to several (e.g., Nikon) DSLRs, and they show low-light performance very comparable to same-format DSLRs. Olympus m4/3 cameras also perform just fine, with allowance for the smaller sensor size.

Ah- this is helpful. As I said, different manufacturers implement technologies in their own way. The Sony A7 series embeds the AF sensor into the main image sensor, so there's no pickoff and no loss of light. Similarly, use of an electronic front curtain shutter allows for elimination of one of the mechanical shutters (I think a back curtain shutter is still required).

https://www.mhohner.de/newsitem2/efcs
 

1. What is a DSLR camera and why should I consider buying one?

A DSLR (Digital Single Lens Reflex) camera is a type of digital camera that uses a mirror and prism system to reflect light from the lens into the viewfinder, allowing you to see exactly what the lens sees. This makes it easier to compose your shots and get accurate focus. Additionally, DSLR cameras have larger image sensors and interchangeable lenses, allowing for higher quality images and more creative control over your photography.

2. What should I look for when choosing a DSLR camera?

When choosing a DSLR camera, there are several factors to consider. First, consider the camera's sensor size, as larger sensors typically produce higher quality images. Next, look at the camera's resolution, or number of megapixels, which affects the level of detail in your photos. Other important features to consider include autofocus capabilities, ISO range, and shooting speed.

3. Are DSLR cameras better than point-and-shoot cameras?

It depends on your needs and preferences. DSLR cameras generally offer better image quality, more manual control over settings, and the ability to use interchangeable lenses. However, point-and-shoot cameras are often more compact and easier to use for casual photography. Consider your photography goals and budget when deciding between a DSLR and point-and-shoot camera.

4. How important is the camera brand when purchasing a DSLR?

The brand of a DSLR camera is not the most important factor, as there are many reputable brands that produce high-quality cameras. Instead, focus on the specific features and capabilities of the camera itself. It's also a good idea to read reviews and compare different models within your budget to find the best fit for your needs.

5. What accessories do I need for my DSLR camera?

The necessary accessories for a DSLR camera will vary depending on your specific photography needs. However, some essential accessories may include lenses, a camera bag, extra batteries, and a tripod. Other useful accessories could include a flash, filters, and a remote shutter release. Research and consider what accessories would be most useful for your photography style and budget.

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